Headlines overnight on that fast-moving ebola outbreak. New warnings out and many people wondering if it could trigger an even bigger epidemic. Latest Numbers coming in. 1,323 cases right now. 729 deaths. ABC's bazi kanani is tracking it all from Washington. Good morning, bazi. Reporter: Good morning, George. String gent new measures to contain the outbreak. In Liberia, schools are now closed until further notice. And everyone is being ordered to stay home this Friday while public facilities are disinfected. In west Africa this morning, doctors screen airline passengers as fears mount about the spread of the worst ebola outbreak in history. If we don't fight it and contain it there we will be fighting it and trying to contain it in other places. Reporter: Here in the U.S. High alert at hospitals like one in Charlotte, the er closed Wednesday until doctors cleared a patient who had recently traveled to west Africa. A false alarm for one family, but not for another in Minnesota. Patrick sawyer died just weeks before returning from Liberia. I have three girls who will never get to know their father. Health care providers who have come in contact with patients or in close contact with ill people are at the highest risk. Reporter: The concern about the outbreak intensifying just as some 50 african leaders and their Dell gag, some from affected countries, are set to travel to the U.S. For a u.s./africa summit next week. The CDC says there is not significant risk here in the U.S., yet, some in the medical community urge caution. I think we should be on alert. I don't want to cause panic but people need to be concerned and pay attention. Reporter: The white house says the ebola outbreak does not change any plans for the historic u.s./africa leader shument but the presidents of the three most affected countries are canceling their trips expected to stay home to deal with this health emergency. George. A lot to deal with. Bazi, thanks. Let's talk to Dr. Richard Besser about this. This is the worst outbreak of ebola ever as we have heard. You see the african nations struggling to control it. That's right. One of the big problems here, usually these occur in remote villages and you can isolate it and let it burn itself out. Here's it's on the border of three countries and unable to get people to go to the hospital and track people who may have been in contact. We also read, you know, one of the researchers who discovered the virus more than 30 years ago came out with an interview saying he would happily sit next to an infected person on a train. I would not want to sit next to someone who is infected on a train but his point is a good one. This is not infectious in the way that the flu is or measles spreading through the air. You see these suits and think it's highly contagious but the reason you wear the suit is that there's no vaccine to protect you and no treatment if you're to get it and it's highly deadly. This is not spread except through close contact with body fluids or surfaces that have been contaminated. The U.S. Has temporarily withdrawn peace corps volunteers this those countries but you are awe not terribly concerned about the spread here to the united States. I would not be surprised if we see isolated case as rife here. You can have no Simms for three weeks after you've been infebruaried but those cases would not spread it around the country. We have good hospitals and good infection control. Okay, rich Besser, thanks very much.

This transcript has been automatically generated and may not be 100% accurate.

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